Methods and techniques in channel assignment in a cellular network

ABSTRACT

A cellular network configuration tool is described that performs frequency assignments for use in a cellular network. The channels are assigned in accordance with input configuration data such as a channel separation matrix, geographic data, and requested channel assignments for each sector included in the cellular network being configured. The configuration is performed in accordance with predetermined constraints and criteria and quality of service input. The tool uses frequency assignment techniques to perform the channel assignments in accordance with varying constraints and criteria.

RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.09/464,301, filed Dec. 15, 1999, and having inventorship and Assignee incommon.

BACKGROUND

1. Field of the Invention

This application generally relates to cellular networks, and moreparticularly to techniques for planning and tuning a cellular network.

2. Description of Related Art

Cellular networks may be used in a variety of applications. For example,cellular networks are used in cellular telephone communications.Cellular networks include, for example, digital and analog cellularnetworks that operate in accordance with one or more protocols orstandards, such as Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), IS-95, or Advanced Mobile Phone Service(AMPS). Generally, cellular networks are configured prior to operationin accordance with certain quality standards, conditions andconstraints. Examples of the foregoing include, minimizing interferenceto base stations or sectors. Additionally, the FCC defines frequencyranges that may be assigned and used for transmissions in cellularnetworks. A base station may be defined as including one or moresectors. Each sector may be viewed as a point from which, or throughwhich, transmissions within the cellular network may be made.

One problem with cellular networks is how to configure the cellularnetwork having multiple sectors, and assigning or associating channelsor frequencies with each of these sectors. In other words, part of theconfiguration of the cellular network is defining at what frequenciesdifferent sectors may operate. Sectors may be assigned channels relatedto information transmissions, such as cellular telephone calls, as wellas particular ones for communications related to transmission set up.This association of one of more of one or more channels or frequencieswith each of the sectors is determined prior to operation of thecellular network. Additionally, only certain ranges may be used asdefined, for example, in accordance with FCC regulations. The FCCdefines bands of frequencies that include a limited number of channelswhich are divided among the various sectors within the cellular networkfor transmissions.

In a heavily loaded cellular system, the limited number of frequenciesor channels may be a problem. One solution is to reuse certainfrequencies and assign the same frequency or channel to more than onesector. However, reusing channels when configuring the cellular networkmay cause the task of system configuration to become increasinglycomplex due to the constraints that are considered in systemconfiguration. For example, two sectors which are adjacent may generallynot be assigned the same frequency due to the extensive interference andoperational problems that may be introduced.

Consequently, part of the process of configuring a cellular network mayinclude determining what frequencies may be reassigned to which sectorswhile trying to minimize the interference which may be introduced byhaving multiple sectors or base-stations operating at the samefrequency. Determining which frequencies may be reassigned or associatedwith multiple sectors is considered in accordance with quality ofservice standards, for example, such that a signal is transmitted at acertain power with minimal interference.

Thus, there is required a technique for configuring a cellular networkin accordance with input configurations constraints as well as qualityof service constraints to achieve a high degree of quality signals byminimizing the interference in a specific set of output configurationdata.

SUMMARY OF THE INVENTION

In accordance with principles of the invention, disclosed is a methodexecuted in a computer system for determining selection criteria inperforming channel assignments in a cellular network. A first timeestimate is determined for a single channel assignment in accordancewith a first set of selection criteria. A total time estimate isdetermined using said first time estimate. A determination is made as towhether the total time estimate is acceptable in accordance with apredetermined time threshold.

In accordance with yet another aspect of the invention is a method andcomputer program product for determining a channel assignment. A set ofassignment criteria is selected in accordance with a predetermined levelof complexity. For each pair of sectors, it is determined whether eachpair are probable neighbors. Pairwise carrier to inteference values aredetermined for each pair of sectors if the pairwise carrier tointerference values are included in the selected set of assignmentcriteria. A channel assignment is determined using the probableneighbors and the pairwise carrier to interference values in determiningwhether to perform a channel assignment.

In accordance with yet another aspect of the invention is a method andcomputer program product for determining carrier to interference values.A set of assignment criteria is selected in accordance with apredetermined level of complexity. Pairwise carrier to interferencevalues are determined for each pair of sectors in accordance with theset of assignment criteria. Total carrier to interference values aredetermined by combining the one or more pairwise carrier to interferencevalues.

In accordance with yet another aspect of the invention is a method andcomputer program product for determining a channel assignment for use ina cellular network. One or more assignment criteria is selected from aplurality of assignment criteria options. The channel assignment isdetermined, in accordance with the one or more assignment criteria,using carrier to interference values and a predetermined thresholdrepresenting a quality of service criteria.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become moreapparent from the following detailed description of exemplary embodimentthereof taken in conjunction with the accompanying drawings in which:

FIG. 1 is an example of an embodiment of a cellular network when acellular device is turned on initially;

FIG. 2 is an example of the system of FIG. 1 when the cellular deviceselects a sector for a transmission;

FIG. 3 is an example of the system of FIG. 1 when a cellular device isnotified of the selected channel for the transmission;

FIG. 4A is an example of an embodiment of a system that may be used toconfigure a cellular network;

FIG. 4B is an example of an embodiment of a computer system as may beused to produce portions of a cellular network configuration tool.

FIG. 5 is an example of an embodiment of the input configuration data;

FIG. 6 is an example of the partitioning of channel assignments;

FIG. 7 is an example of the embodiment of the configurator of FIG. 4;

FIG. 8 is an example of an embodiment of a best server map;

FIG. 9 is an example of an embodiment of the representation of the bestserver regions;

FIG. 10 is another example of an embodiment of the representation of thebest server regions;

FIG. 11 is an example of an embodiment of a flowchart of a method of howto determine probable neighbors;

FIG. 12 is an example of an embodiment of a flowchart of the methodsteps for determining total and common boundaries for contiguousregions;

FIG. 13 is an example of an embodiment of a flowchart of determiningprobable neighbors in accordance with total and common boundaries and aboundary threshold;

FIG. 14 is a flowchart of an example of an embodiment of steps of amethod used in performing C/I calculations in frequency assignments;

FIG. 15 is an example of a flowchart of more detailed sets fordetermining pairwise C/I calculations;

FIG. 16 is an example of an embodiment of the various formulas as may beused in performing C/I calculations;

FIG. 17 is an example of an embodiment of a graphical representation ofa probability density function;

FIG. 18 is an example of an embodiment of a flowchart of method stepsfor performing channel assignments using C/I calculations;

FIG. 19 is a flowchart of an example of an embodiment of another methodfor performing channel assignments and adjustments of criteria inaccordance with previous iterations;

FIGS. 20A, 20B are an example of an embodiment of a table includingvarious selection and adjustment criteria.

FIG. 21 is an example of an embodiment of additional selection criteriastored in a table;

FIG. 22 is an example of an embodiment of a table representing variouslevels of complexity options in accordance with different selectioncriteria.

FIG. 23 is a flowchart of an example of an embodiment of a method fordetermining acceptable selection criteria used in performing channelassignments;

FIG. 24 is an example of a representation of C/I calculations that maybe used when performing color code assignments; and

FIG. 25 is a flowchart of an example of an embodiment of a method ofperforming color code assignments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIG. 1, shown is an example of an embodiment of asystem of a cellular network. The system 170 includes four sectors orbase stations A, B, C and D. Shown in FIG. 1 is the operation oftransmission within the system 170 when a cellular device is turned on.The signals 172, 174, 176 and 178 are transmitted by each of the sectorsor base stations to the cellular device. Generally, the cellular deviceturns on and “listens” for signals 172-178 as transmitted from each ofthe sectors.

It should be noted that the cellular device may include, for example, acellular telephone or other device which transmits signals in a cellularnetwork. Each of the sectors A through D have stations that operatewithin the cellular network 174 for transmissions between the cellulardevice and the sectors, such as making telephone calls from a cellulartelephone.

It should be noted that other embodiments of a system 170 may includemore base stations and sectors, as well as include multiple cellulardevices in operation. The system of FIG. 1 is shown for simplicity asincluding only four sectors and a single cellular device in operation.

Referring now to FIG. 2, shown is a “snapshot” of the system 170 after acellular device is turned on and listens to signals from sectors Athrough D. Once the cellular devices receives a signal from each of thesectors, the cellular device selects one of the sectors for handling itstransmission. As shown in FIG. 2, this selection is performed by thecellular device transmitting a signal to one of the sectors. In oneembodiment, the selection may be based in accordance with the strengthof the signals sent from each of the sectors. The cellular device may,for example, select the sector having the strongest signal transmissionas detected by the cellular device.

Referring now to FIG. 3, shown is an example of an embodiment of system170 with the cellular device being notified by the selected sector ofthe selected channel assignment for transmissions between the cellulardevice and the sector. The sector chooses one of the assignedfrequencies or channels associated with the selected sector. Thesechannels associated with each sector may be predetermined in accordancewith criteria prior to operation of the cellular network 170. The sectorcommunicates to the cellular device as to the selected channel for usein transmitting signals to and from the cellular device.

It should be noted that the embodiment of the system 170 in FIGS. 1through 3 is an example of a communications or transmission protocolthat may be used in communicating with a cellular device. It should benoted that prior to operation as in performing the signal transmissionsbetween the base stations or sectors and a cellular device in operation,the system 170 must be properly configured in accordance with selectedsets of channel assignments or frequencies. In particular, each of thebase stations A, B, C and D are associated with a set of frequencies orchannels which may be assigned or used when transmitting to and from acellular device as indicated in the system of FIGS. 1 through 3 when acellular device is in operation.

As known to those skilled in the art, the FCC defines certain channelsor frequencies that may be assigned or used in transmissions within acellular network. There is a relatively small number of channels orfrequencies that may be assigned. Thus, part of the problem ofconfiguring the system 170 includes how to divide the different channelsthat are used within the cellular network. Various tools, such as GRANET(“Graphical Radio Network Engineer Tool”) as used by GTE Corporation maybe used to configure and tune cellular systems,such as the system 170 ofFIGS. 1-3.

What will be described in paragraphs that follow are techniques fortuning and configuring this system in accordance with certain input dataand criteria or constraints. For example, the constraints may relate toquality of service, such as requiring information transmissions to be ofa certain power level. Various input configuration information, such asthe geographic constraints, is also considered when doing channelassignments and information transmissions. It should be noted that otherconstraints and input may be considered as known to those skilled in theart, for example population, in a particular area. Population may be anindicator of the number of channel assignments required for a particularsector.

Referring now to FIG. 4A, shown is an example of an embodiment of asystem 10 that may be used to configure the cellular network 170 of FIG.1. The system 10 includes input configuration data 16 which is input toa configurator 12 producing output configuration data 14. The inputconfiguration data, as previously described, may include constraints ofa particular system, as well as quality of service (QOS) parameters orrequirements. This will be described in more detail in paragraphs thatfollow. Given a particular set of input configuration data, theconfigurator 212 produces an output configuration data set 14.Generally, the output configuration data 14 is that information which isneeded to configure the particular sectors such as those A through D inthe system 170 operating in the cellular network. In particular, theoutput configuration data includes one or more channels selected andassociated with a particular sector. As previously described, thesechannel assignments or frequencies are those which may be used by thevarious sectors in transmissions between a cellular device operatingwithin a cellular network 170.

Referring now to FIG. 4B, shown is an example of an embodiment of asystem which may be used in producing a configuration for the cellularnetwork 170 of FIG. 1. In this particular embodiment, the configurator12 as well as the input configuration data 16 and output configurationdata 14 may reside on a storage device 20 connected by connection 19 tocomputer system 18. The computer system 18 may be any commerciallyavailable processor such as an Intel based personal computer or othercommercially available computer system in accordance with eachparticular implementation. The communication connection 19 may be anetwork connection or other type of connection between a storage device20 and a computer system 18 upon which a configuration 12 may beexecuted to produced the output configuration data 14. It should benoted that portions of the configuration 12 which should be described inparagraphs that follow may be implemented in software and/or hardware.Those particular portions which are software may be located and storedin a storage device such as 20 and transferred for execution to computersystem 18 through connection 19. A variety of different types ofconnections 19 are known to those skilled in the art and may vary witheach particular embodiment.

It should also be noted that, similar to the variety of networkconnections and computer systems that may be used in a particularembodiment, a variety of data storage devices 20 may be included in theparticular embodiment as known to those skilled in the art.

Referring now to FIG. 5, shown is an example of an embodiment ofdifferent classifications of input configuration data 16. Inputconfiguration data 16 includes geographic data 22, with requestedchannel assignments 30, and the channel separation matrix 24. Generally,the geographic data 22 may include a variety of information describingthe geographic locale, such as the terrain of an area, which may be usedin propagation modelling, as well as particular antenna characteristicsas used in operation within a particular sector. Additionally, inputinformation related to geography may include information aboutpopulation as well as various land characteristics. In this particularembodiment, the geographic data includes base station or sector locationinformation, such as longitude and latitude and tower height. Alsoincluded in the geographic data is a representation of the contour ofthe land, for example, in the form of raster maps. Additionally,geographic data may include information regarding the elevation of theland as well as land use and cover, such as whether a particular area isresidential, an orchard, or over water.

Generally speaking, the input configuration data includes that inputinformation which may be relevant to a particular embodiment and shouldbe considered when determining the configuration of the cellularnetwork. Requested channel assignments 30 is basically a request of thenumber of frequencies or channels to be associated with each particularbase station or sector. Generally, channel assignments may be determinedfor example by estimation using the population information or it may bealternatively be based on past use. It should be noted that the types ofinformation included in each of the foregoing may vary with embodimentin accordance with each particular application and implementation.

The channel separation matrix 24 is a representation of the minimumchannel separation between any two base stations or sectors. In thisparticular embodiment in the channel separation matrix 24, an N×Ndimensioned matrix may be used. In this embodiment there are N basestations or sectors. Each entry in the matrix represents the minimumchannel separations between the two sectors as indicated by,respectively, a particular row and column pair. Typical entries in thematrix are one of a 0, 1 or a 2. A channel separation of 0 indicatesthere is no separation between frequencies or channels that may beassigned to particular base stations. A 1 indicates that there must beat least a plus or a minus of 1 channel difference in assignmentsbetween two particular sectors. Similarly, a 2 indicates that noadjacent sectors may be assigned the same frequency or channel.

Generally, the term “neighbor” is used to describe how one sector andits base stations relates to another sector and its base stations. It isgenerally known in the art that if a call may be “handed off” to asector from another sector, those two sectors may qualify as neighbors.With regard to the channel separation matrix, a neighbor may bereflected in the channel separation matrix by a minimum separation of 2indicated between a pair of sectors or base stations.

Referring now to FIG. 6, shown is an example of an embodiment of thefour sets of channel assignments that may be performed within anembodiment of the system of the cellular network 170. In other words,the configurator tool 12 may be used to select particular channels orfrequencies and accordingly associate them with different sectors. Forexample, in AMPS, the four sets of channel assignments include trafficchannels 32, set-up channels 34, Supervisor Audio Tones (SATs) 36, andDigital Color Codes (DCC) 38.

Generally, traffic channels 32 are those channels or frequenciesassigned or associated to a particular sector for transmissions when inoperation. These channels may generally be described as operationtransmission frequencies, for example, those frequencies that may beused in information transmissions between a cellular device and a sectorduring transmission of a cellular telephone call. Set-up channels 34 arethose channels each associated with a sector at which the sector mayoperate to set-up an initial communication with a cellular device. Forexample, referring to FIG. 1, each of the transmissions 172 through 178operate at a particular set up frequency or channel associated with eachof the base stations A through D. Generally, the techniques that will bedescribed to configure the traffic channel calls may also be used toconfigure the set-up channels.

The SATs are generally an assignment of one of three particular tonesassociated with each frequency or channel assigned, and assist with theidentification of a particular base station or sector. The DCCs relateto the set-up channels between a base station and a handset or cellulardevice. The DCC is two bits of information assigned to each set-upchannel and placed into in the transmission stream.

Referring now to FIG. 7, shown is an example of an embodiment of theconfigurator 212 of FIG. 4. Generally, FIG. 7 shows a flow diagram ofthe various components and how they operate and interact within theconfigurator 212. This embodiment of the configurator 212 includes apropagation module 40, a pairwise C/I module 42, a best server module44, a probable neighbors module 46, a channel separation matrix module48, and a frequency assignment module 50. Input to the propagationmodule includes a portion of the input configuration data, such asgeographic data. Generally, the propagation module 40 determines howstrong a signal from a sector, or base station from within a sector, isfrom any place in a region. This propagation or signal strength is usedto compute path loss. Information regarding signal strength is input tothe best server module 44 and the pairwise C/I module 42. This bestserver module 44 may determine the best server regions for the operationof the cellular network. In other words, the best server module 44determines which base stations or sectors may best handle an incomingcall or transmission in accordance with the signal strength asdetermined by the propagation module 40.

The best server region indicates for a particular area what base stationor sector is best suited to handle or serve calls from that particularregion. The best server region module 44 is used to determine the bestsector to serve or handle an incoming call in accordance with signalstrength. The pairwise C/I module 42 performs determinations inaccordance with hypothetical or simulated conditions, e.g., a “what if”scenario, that are considered when assigning frequencies or channels.The pairwise C/I module 42 determines the strength of a signaltransmitted at a frequency if sectors A and B are both assigned the samefrequency and if no other frequencies are assigned. Generally, thepairwise C/I considers what the strength of a signal from a first sectoroperating in a first frequency or channel in conjunction with theinterference generated by a second sector also operating at that samefrequency or channel. Generally, the pairwise C/I considers thehypothetical situation in this assignment as a condition in determiningwhether to perform a certain frequency assignment as an input to thefrequency assignment module 50. Determining frequency assignments fromthe pairwise C/I module 42 is used by looking at each point in a bestserver region and considering the strength of the desired or carriersignal as well as the strength of the interference. This will bedescribed in more detail in paragraphs that follow. It should generallybe noted that the pairwise C/I requirements produced by the pairwise C/Imodule 42 in considering frequency assignments relate to quality ofservice. In other words, the pairwise C/I module 42 produceshypothetically input in accordance with a particular channel assignmentconfiguration. This may generally be viewed as an estimation ofinterference as related to a particular frequency assignment. This isconsidered as an input to the frequency assignment module 50 inconjunction with the quality of service input 54 which dictates, forexample, quality of service required for a particular systemconfiguration. The pairwise C/I module 42 considers the interferencecomponents for hypothetical pairs of frequency assignments.

Output produced by the best server module 44 is also input to theprobable neighbors module 46. Generally, the probable neighbors module46 may be used to produce input to determine what two sectors are, ormay be considered, “neighbors”. This is used as input in producing thechannel separation matrix by the channel separation module 48.Additionally, switch neighbor data 52 may also serve as an input inproducing the channel separation matrix by module 48. Generally, switchneighbor data is a snapshot of the channel separation as known to theexisting switching systems as may be included in an embodiment of thesystem 170 of FIG. 1. It should be noted that both actual switchneighbor data 52 as well as output from the probable neighbors module 46may serve as input to the module 48 in producing the channel separationmatrix. The switch neighbor data 52 represents the actual description ofwhat sectors are considered neighbors by the switches currently inoperation. However, it is often the case that an embodiment may want toadd sectors or base stations. Thus, performing using the actual switchneighbor data 52 does not suffice to accurately describe the neighborrelationship between all sectors in this instance. For example, where anadditional base station or sector is to be added, input for this futureconfiguration may come from the probable neighbors module 46 and serveas input for module 48 to produce the channel separation matrix aspreviously described.

In this embodiment, the channel separation matrix may includeinformation as will be described below. Generally, two sectors have aminimum separation of 2 if a call can be “passed off” between the twosectors, qualifying the two sectors as neighbors. If two sectors havethe same neighbor, for example sectors C and D may have a commonneighbor A, then C and D have a separation of 1 as may be indicated inthe channel separation matrix. Otherwise, a zero (0) is indicated as anentry in the channel separation matrix by the switch neighbor data 52. Achannel separation matrix may be used as an input to the frequencyassignment module 50. Generally, the frequency assignment module 50takes into account those sectors which are neighbors as well ashypothetical interference in accordance with a particular frequencyassignment. The frequency assignment module 50 uses this information toproduce a configuration of channel assignments associated with eachparticular sector, for example, in producing the traffic channelassignment set 32.

Additionally, threshold tests may be made in accordance with QOS input54 such that a particular configuration operates in accordance withpredetermined QOS requirements 54. The frequency assignment module 50outputs configuration data, for example, such as traffic channelconfiguration information 32 of FIG. 6 which associate each particularsector with one or more frequency or channels for transmissions. Each ofthe components for the system 12 of FIG. 7 will be described in moreparagraphs that follow.

Referring now to FIG. 8, shown is an example of an embodiment of thebest server map. The best server map 100 in FIG. 8 includes informationabout what is the best server for handling a particular call in a regionwithin the cellular network. The representation of the best server map100 includes a cell associated a particular portion of geographic area.For example, in the best server map 100, a global geographic area isassociated with cell 2 for which sector A is indicated as the bestserver. Similarly, sector A is indicated as the best server associatedwith the geographic area of cell 17. However, sector B is indicated asthe best server for the geographic area associated with cell 3, 4 and18. It should be noted that some particular geographic areas, such asindicated by geographic area 20, in this representation with an X has nobest server associated with that particular geographic location.

It should also be noted that indication of the same best server may bescattered throughout the best server map. In other words, there areareas or portions of the best server map which may not be contiguous inrepresenting those portions for which A, B C, or D are the best servers.For example, note that cell number 5 contains an A and cell numbers 3and 4 contains B's. Thus, those geographic areas associated with cellnumber 5 indicate A is the best server. However, this is separate from,and not contiguous with, that portion of the map defined by 110 whichincludes a block or group of cells shown in the left portion of the map100. In particular, the area 110 represents a contiguous portion of thebest server map for which A has been designated the best server. Thisportion 110 is disjoint and separate from other single cells, such ascell number 5 and cell number 27 that also indicate A as the bestserver.

Generally, such disjoint representations may occur, for example, due tovarious geographic details such water, land or particular urban areas.For certain geographic locations such as those with certain elevation ormountainous terrains, there may be disjoint best server groupings orgaps between those geographic areas associated with the same bestserver.

Referring to FIG. 9, shown is an example of a pictorial representationof the best server regions. The best server regions for each of thesectors or base stations A through D are indicated respectively by thecircular regions 120 through 126. It should be noted that thisrepresentation indicates only contiguous areas in a smooth fashion.However, as previously discussed in conjunction with FIG. 8, it is oftenthe case that best server regions are not representable in such graphicrepresentation as ideally given in FIG. 9, for example, due to thedisjoint best servers regions associated with a particular geographiclocation.

Referring to FIG. 10, shown is another example of a pictorialrepresentation of the best server region associated with each of thesectors A through D as included in the system 170 of FIG. 1. Note thedifference between the regions 130 through 136, respectively, with thoseregions indicated by 120 through 126.

Referring to FIG. 11, show is an example of flowchart of the methodssteps for determining probable neighbors. Generally, the method steps ofFIG. 11 in flowchart 140 are those that may be performed by the probableneighbors module 46 in determining which pairs of sectors are probableneighbors. As previously described, the probable neighbors module 46implements a technique which is intended to be used when the switch data52 may be unavailable or out of date for a particular sector beingconsidered. As previously described also, this may be used as analternative, for example, when a new sector is being added for whichthere is currently no active switch data 52 available.

At step 142, the contiguous regions of the best servers are determined.As previously described in conjunction with FIG. 8, in this embodimentthe best server map is examined to determine which portions arecontiguous within the map indicating a contiguous region or geographicarea for which a common best server has been indicated. This may beindicated for example by the graphical representation of portion 110 ofmap 100 which indicates A as the best server for the associatedgeographic area.

At step 144, the total and common boundaries of the contiguous regionsare determined. In other words, the total boundary for a particularcontiguous region such as 110 is determined. This may be indicated, forexample, by the darkened line surrounding the portion 110 of map 100,indicating the total boundary for this contiguous region. Alsodetermined at step 144 is that portion of the boundary which is commonbetween two contiguous regions in which each contiguous indicates adifferent server. In this example, line 111 indicates a common boundaryfor example between the contiguous area 110 and another contiguous areawhich has not been defined and determined in the best server map 100.

At step 146, probable neighbors are determined in accordance with totaland common boundaries as well as a predetermined boundary thresholdvalue. What will now be described in paragraphs that follow are moredetailed descriptions for the steps of the flow chart 140 of FIG. 11.

Referring now to FIG. 12, shown is a flowchart of an embodiment of amore detailed step 144 for determining total and common boundaries ofcontiguous regions. At step 160, the total boundary is determined foreach sector. In other words, at step 160, a total boundary orquantitative representation is determined representing the boundaryconditions for each sector as indicated in the best server map 100. Atstep 162, the common boundaries between each pair of sectors aredetermined.

Referring now to FIG. 13, a flowchart is shown to include more detailedsteps for determining probable neighbors in accordance with total andcommon boundaries as well as a predetermined boundary threshold value asindicated in step 146 of the flowchart 140. At step 162, it isdetermined for each pair of sectors A and B having a common boundary theratio or percentage of common sector boundary to total sector boundary.In other words, a percentage is arrived at with the numerator as thecommon sector boundary over the total sector boundary for each pair ofsectors A and B. In one particular embodiment, the total sector boundarymay be either the total sector boundary regarding best server A or thetotal sector boundary regarding best server B. One embodiment mayconsider the minimum of the total sector boundary of either A or B.Another embodiment may take the maximum of the total sector boundary ofeither A or B. Other embodiments may use other values in the ratio. Atstep 162, a decision is made comparing each of these percentages orratios for a pair of sectors having a common boundary to a predeterminedboundary threshold.

At step 162, it is determined for each pair of sectors A and B having acommon boundary, is the common boundary or percentage of the commonboundary to the total boundary greater than some threshold for both thetotal boundaries of A and B. If it is determined at step 162 that such acondition is true, control proceeds to step 166 where it is determinedthat sectors A and B are probable neighbors due to the large percentageof common boundaries shared between the two sectors indicated by thepair A and B. If it is determined at step 162 that the portion of commonboundary between A and B is less than or equal to the boundary thresholdfor both the total boundaries of A and B, control proceeds to step 164where it is determined that sectors A and B are not probable neighbors.

Included below is a pseudo code representation of an implementation ofthe probable neighbors technique generally described in the flowchartsof FIGS. 11 through 13. Prior to setting forth this pseudo codedescription, certain assumptions and data representations will now bedescribed. The array best_server[place] is a representation of a bestserver for any pixel. Generally, the array best_server contains anidentifier for the sector determined to be the best server associatedwith particular places indicated by the index into the array. It isassumed that a function not₁₃ a_best_server (place) returns a value oftrue when the corresponding pixel is not a best server as indicated bythe parameter place. Similarly, it is assumed in the pseudo codedescription that a function over_water (place) returns a value of truewhen the corresponding pixel is over water. Such pixels are ignored inthe probable neighbors calculation. The functions find_row (place) andfind_col (place) return the row and column respectively at any pixel.The function find_pixel (row, col) returns a pixel given a particularrow and column. The use of pixels in this particular example are thoughtof as components of a raster scan representing the geographic area. Thisrepresentation in a raster type of image is a convenience rather than anecessity in using the techniques of this. Pixels may be scanned frommap_start to map_end. Each row has a row_start and a row_end. Eachcolumn has a col_start and a col_end. A local array pixel_flag[place] isgiven values of sector identifiers. These include special values ofIGNORE, UNPROCESSED and PROCESSED that are distinguishable from allsector identifiers and each other. Sectors may be scanned in order fromfirst_sector to last_sector. Probable neighbors may be returned in amatrix as indicted in the pseudo code as neighbor_matrix with a 2dimensional index [sector A, sector B]. The neighbor_matrix contains anentry of 1 if the corresponding pair are probable neighbors and an entryof 0 otherwise. A temporary stack is assumed to be available for pixelsusing the foregoing techniques to find and mark fragments includingchecking for and protecting against stack overflows.

Includes below is the PROBABLE_NEIGHBORS pseudo code.

PROBABLE NEIGHBORS( ) /* *Set small gap threshold */ boundary_width =200m   /* default value for gap threshold*/ width = max((floor(boundary_width/unit_x) + 1/2), 1)/* convert to pixels */ /* *Set“common boundary threshold */ boundary_fraction = .05   /* definedefault threshold for “common boundary” */ /* *Initialize */ for place =map_start to map_end /* scan by pixels */ if not_a_best_server (place)or over_water (place) pixel_flag[place] = IGNORE else pixel_flag[place]= UNPROCESSED /* * Find Largest contiguous region for each server */ forplace = map_start to map_end if pixel_flag[place] = UNPROCESSED best =best_server[place] biggest_size = 0 for new_place = place to map_endif(pixel_flag[new_place] = UNPROCESSED and best_server[new_place]= best)/* *Find all pixels contiguous with current one */ size_fragment =find_fragment(new_place,best,width,pixel_flag) if biggest_size <size_fragment biggest_size = size_fragment biggest_place = new_place /**Mark smaller fragments as seen/processed in largest contiguous region*/ for new_place = place to map_end if pixel_flag[new_place] = PROCESSEDif new_place = biggest_place flag = best /* mark biggest fragment bybest server */ else flag = IGNORE /*ignore other fragments*/mark_fragment (new_place,best,width,pixel_flag,flag) /* /* finding sizeof border */ for sector_a = first_sector to last_sector /* *Initiaiizefor sector_b = first_sector to last_sector n_pixels[sector_a, sector_b]= 0 neighbor_matrix[sector_a, sector_b] = 0 for place = map_start tomap_end if pixel_flag[place] NOT_EQUAL IGNORE sector_a =pixel_flag[place] /* *conversion between pixels and rows and columns */row = find_row(place) col = find_colplace) /* *look to the east forcounting pixels in the border */ for other_col = col+1 to min(col+width_1, col_end) other_place = find_pixel(row,other_col) ifpixel_flag[other_place] NOT_EQUAL IGNORE sector_b =pixel_flag[other_place] /* *boundary is found */ if sector_a NOT_EQUALsector_b n_pixels[sector_a, sector_b]++ /* *look to the north forcounting pixels in the border */ for other_row = row+1 tomin(row+width+1, row_end) other_place = find_pixel(other_row,col) ifpixel_flag[other_place]NOT_EQUAL IGNORE sector_b =pixel_flag[other_place] /* *boundary is found */ if sector_a NOT_EQUALsector_b n_pixels[sector_a, sector_b]++ /* *Symmetrize counts and sumsover border - if a-b is border, so is b-a */ for sector_a = first_sectorto last_sector for sector_b = first_sector to last_sector if sector_a <sector_b n_pixels[sector_a, sector_b] = n_pixels[sector_a, sector_b] +n_pixels[sector_b, sector_a n_pixels[sector_b, sector_a] =n_pixels[sector_a, sector_b] if sector_a NOT_EQUAL sector_bn_pixels[sector_a, sector_a] = n_pixels[sector_a, sector_a] +n_pixels[sector_a, sector_b] /* *not neighbors of the border doesn'tmeet threshold requirements */ for sector_a = first_sector tolast_sector for sector_b = sector_a+1 to last_sector /* *thisimplementation is conservative - total boundary threshold is thesmallest total boundary *length of base station/sector pair */boundary_length_threshold = max(boundary_fraction *min(n_pixels[sector_a, sector_a], n_pixels[sector_b, sector_b]) ifn_pixels[sector_a, sector_b] >= boundary_length_thresholdneighbor_matrix[sector_a, sector_b] = 1  /* A and B are neighbors == 1neighbor_matrix[sector_b, sector_a] = 1  /* they are neighbors == 1/*********************************************************************/

The foregoing pseudo code generally identifies a connected set of pixelsfor each best server. Sectors with neighboring sets of pixels aredetermined to be probable neighbors. In this embodiment, best serverareas are notably fragmented at the pixel level. In particular, aspreviously discussed in conjunction with a best server map, a phenomenonthat may be termed speckling may occur in which isolated pixels far froma sector have an indication of the same best server. This is in fact anartifact, for example, of small fluctuations in path loss estimation,and such isolated pixels may be excluded from probable neighborscalculation. In one embodiment, best server areas may be composed of anumber of disconnected fragments each of which appears to the eye as aconnected whole. For computation of contiguous regions, this may beformalized or taken into consideration. A fragment may be defined as amaximal set of piecewise connected pixels with the same best server. Thepixel is in a fragment if and only if it is within the boundary width ofat least one other pixel in the fragment. These fragments may be foundby the find fragment function which will be described in more detailbelow. The point of the boundary in the probable neighbors in theprobable neighbors pseudo code is to unify fragments which may beseparated by insignificant gaps. As indicated in the pseudo code, thecurrent default value for such a gap is 200 meters. Other values mayalso be used.

In order to consider in an embodiment the fact of widely scatteredfragments which may introduce spurious probable neighbors, only thelargest fragment for each best server is considered in the foregoingpseudo code. This is done by means of the MARK_FRAGMENT function whichwill also be described below.

Once a single fragment is identified for each best server, the number ofneighboring pixels with all other best server fragments is counted. Aneighboring pixel is one within the boundary along the east-west ornorth-south line. The point of the boundary in this particular exampleis to remove the effect of insignificant gaps. Best server regions withenough neighboring pixels are deemed probable neighbors. This count mustbe at least as large as a specified fraction of the largest possiblecount in accordance with the predefined threshold. In the foregoingdescription the default value or threshold is indicated at 5%.

Indicated below is the pseudo code for the FIND_FRAGMENT routine whichis used by the probable neighbors pseudo code.

FIND_FRAGMENT(place, best, width, pixel_flag) row_start =find_row(place) /*push starting place onto the stack push(place) size =1 while stack < > NULL new_place = pop( ) row = find_row(new_place)col - find_col(new_place) /*look within width of new_place for connectedpixels, but not before starting row for other_row = max(row-width,row_start) to min(row+width, row_end) for other_col = max(col-width,min_col) to min (col+width, col_end) other_place = find_pixel(other_row,other_col) if pixel_flag[other_place] = UNPROCESSED ifbest_server[other_place] = best pixel_flag[other_place] = PROCESSEDpush(other_place) size++ return(size)/**********************************************************/

The method or technique for finding fragments in best server areas isused in the probable neighbors pseudo code description and may bereferred to as a flooding technique. For any pixel in a fragment, alladjoining pixels with the same best server are also made part of thesame fragment. In this particular example, adjoining is defined as abovewithin the boundary width. As each such pixel is found it is marked asbeing processed and pushed onto the stack. When a pixel is popped fromthe stack, adjoining unprocessed pixels are sought for it. The processstops when the stack is empty, indicating no more unprocessedneighboring pixels can be found. Additionally, FIND_FRAGMENT counts thenumber of pixels within the fragment so that the largest fragment may besubsequently identified as indicated in the probable neighbor pseudocode.

Included below is a pseudo code representation of the MARK_FRAGMENTroutine which may be used in conjunction with the PROBABLE_NEIGHBORS andFIND_FRAGMENT pseudo code.

MARK_FRAGMENT(place,best,width,pixel_flag,flag) row_start =find_row(place) /* push starting place onto stack push (place) whilestack < > NULL new_place = pop( ) row = find_row(new_place) col =find_col(new_place) /* look within the width of new_place for connectedpixels but not before starting row for other_row =max(row-width,row_start) to min(row+width, row-end) for other_col =max(col-width, min_col) to min(col+width, col_end) other_place =find_pixel(other_row, other_col) if pixel_flag[other_place] = PROCESSEDif best_server[other_place] = best pixel_flag[other_place] = flagpush(other_place)

It should be noted that a flooding technique as previously mentionedwith FIND_FRAGMENT is also used to mark fragments in the MARK_FRAGMENTpseudo code pixel by pixel after the largest fragment is identified.That fragment is marked by the sector identifier for the best server.All other fragments are subsequently ignored. In the foregoingdescription of PROBABLE_NEIGHBORS, it should be noted that a thresholdis established as a common boundary percentage. Additionally, a gapthreshold is determined as indicated by the parameter with, both ofthese threshold conditions may be modified in accordance with eachparticular implementation or embodiment. Additionally, the foregoingimplementation only considers the largest contiguous region for eachserver when determining neighboring sectors. It should also be notedthat the foregoing pseudo code implementation of the general flow chartdescribed in conjunction with FIGS. 11 through 13 takes a conservativeapproach when defining or determining whether two sectors are neighbors.This may be indicated by the threshold boundary_length_threshold wherethe threshold considers the smallest total boundary length for the basestation or sectors in the pair. In the foregoing pseudo codedescription, this may be determined by taking the minimum of n pixelswhen computing boundary_length_threshold.

What will now be described are calculations involving the C/I statisticsthat may be computed, for example, by the pairwise C/I module 42 of FIG.7. These calculations may be used, for example, in performing frequencyassignments by the frequency assignment module 50.

The technique that will be described may be used in improving theaccuracy of frequency assignments and channel assignments. Pairwise C/Ivalues may be especially useful as a “figure of merit” for evaluatingvarious frequency assignment scenarios, as may be performed inconfiguring the network 170. This figure of merit may be used to assesschannel quality, and optimize the assignment for total interferencerequirements in accordance with quality service requirements, forexample, as may be input to the channel assignment module.

As previously described, the pairwise C/I may be measured as the ratioof carrier power to interference power between two sectors using thesame channel, or in other words, having the same channel assignment. Twopairwise C/I values exist for every pair of sectors A and B, where A isthe carrier and B is the interferer, as well as where B is the carrierand A is the interferer. As will be described in paragraphs that follow,a data structure, such as a matrix, may be used to store C/I values andother associated data during the channel assignment process.

It should be noted that the interference as expressed in the C/I valuesmay depend on such factors, for example, as coverage areas from thetraffic distribution, and received power distribution. As will bedescribed, it is assumed that measurements of power may be accuratelymodeled as having a lognormal distribution when the short distancefluctuations are averaged out. The power, as may expressed in decibels,is normally distributed with some predicted mean and standard deviationthat are verified by measurements. Consequently, the C/I in decibels isthe difference between two normal random variables with given means andstandard deviations. Hence, the distribution of the C/I is normal. Themean is the difference between the mean carrier power and the meaninterfering power. The standard deviation may be found by knowing thecorrelation co-efficient between the carrier power and the interferingpower.

The statistical correlation that exists between the carrier power andthe interfering power depends on the relative angle of arrival to thegeographic areas being considered. Measurements may indicate that thecorrelation co-efficient, as will also be described, may be empiricallyestimated as a function of the magnitude of the angle between the pathsto the point of interest in a coverage area. In this instance, thecorrelation co-efficient is a maximum of 0.9 at an angle of 0, and dropsoff linearly to 0 at a 180 degrees.

Once a C/I distribution is found at each point, the distribution isweighted proportionally to the estimated traffic for the area in theneighborhood of the point, and averaged over all the points covered bythe carrier sectors coverage area. An overall distribution of C/I isthus formed. The pairwise C/I estimate may be defined as a percentilefrom this distribution, for example, the 10th percentile may be used.

Referring now to FIG. 14, shown is a flowchart of the method steps asmay be used in computing and using C/I calculations in performingchannel assignments. At step 202, pairwise C/I is determined for eachpair of sectors. At step 204, the total C/I is computed for each of thepairwise C/I contributions. The total C/I may be expressed as asummation over pairwise C/I contributions. In this particularembodiment, two types of total C/I computations may be considered whenperforming step 204. These two types may be termed co-channel C/I andadjacent channel C/I calculations. Generally, the total C/I may becomputed for each channel i assigned in a sector j producing somecarrier power to some interference power. This may be termed co-channelC/I. This may be expressed in the following formula:$\left( {C/I} \right)_{j,i} = \frac{1}{\sum\frac{1}{\left( {C/I} \right)_{k,{j\quad {pairwise}}}}}$

where the sum Σ in the above formula is for all k such that channel i isassigned to sector k. It should be noted that C/I_(ji), the left handside of the foregoing equation, is the total interference at sector j onchannel I. Additionally, C/I_(kj) pairwise is the pairwise interferenceat sector j due to sector k.

Similarly, the adjacent channel C/I may be computed as:$\left( {C/I} \right)_{j,i} = \frac{1}{\sum\frac{1}{\left( {C/I} \right)_{k,{j\quad {pairwise}}}}}$

where the sum Σ in the above formula is for all k such that channel i−1or channel i+1 is assigned to sector k. Generally, as will be describedin paragraphs that follow, these two types of total C/I calculationsinvolving co-channel and adjacent channel C/I may be used as C/Iconstraints that may be considered when performing frequency selection,for example, using channel assignments techniques.

At step 206, frequency or channel assignments are performed inaccordance with C/I calculations as performed in step 204. Inparticular, as will be described in conjunction with other Figures, theC/I calculations may serve as constraints in a particular embodiment ofthe system and may affect whether a particular channel or frequency isassigned to a particular sector or sectors. At step 208, a C/I map maybe generated. Generally, the C/I map is produced as an analysis tool forassessing the quality of channel assignments. A C/I map calculation is arepresentation where, for each pixel representing a certain geographicarea, the “worst” assignment made for a particular channel is examined.For example, in one embodiment the “worst” channel assignment may bedetermined in accordance with the weakest signal strength. This mayassist in presenting a graphical representation of how well channelswere assigned to particular sectors in accordance with certain criteria,such as strength for resulting signals, for particular channelassignments.

Referring now to FIG. 15, shown is an example of an embodiment of aflowchart that includes method steps for determining pairwise C/I.Generally, FIG. 15 is a more detailed description of step 202 from FIG.14. At step 220, the probability density is computed for each pixel inthe best server area. At step 222, the probability density is weightedas the function of the amount of teletraffic representing the likelihoodthat someone would make a call at a pixel's associated geographic area.Subsequent to performing the loop of steps 220 and 22 for each pixel,control proceeds to step 224. In other words, step 224 is performedcollectively after steps 220 and 222 have been performed for all pixels.At step 224, pairwise C/I's are determined by choosing a percentile andcomputing a percentile of the distribution previously produced in step222.

What will now be described is determining the pairwise C/I calculationsas may be used in computing the total C/I for co-channel and adjacentchannel constraints in determining whether to perform channelassignments.

Referring now to FIG. 16, shown is a graphical representation of thepairwise C/I calculation for an interfering sector 300 and a carriersector 302. For each map pixel in the best server area indicated, forexample, by a best server map and a sector pair, a C/I distribution iscalculated. Formula 304 represents the relationship for C/I calculationsbeing distributed with a particular mean and standard deviation. Aspreviously described in this particular example for frequency planningas represented by box 314 of FIG. 16, frequency plan parameters arechosen such that this is a log normal distribution having a log normalsigma or standard deviation, and a correlation co-efficient of p=0.9.This may be used, for example, in the formula expressed by box 308 wheresigma_fpp represents the standard deviation of C/I. It should be notedthat there is an assumption of a linear drop-off to use this particularcorrelation co-efficient. Formula 306 relates the mean of formula 304.The mean is assumed to be normally distributed and thus the expectedvalue or mean may be represented as in formula 306 and relates toformulas 310 and 312 also shown in FIG. 16 where N(μ,σ) represents anormal probability distribution.

Referring now to FIG. 17, shown is a graphical representation of anembodiment of the effect of traffic and angular correlation dependancein the overall C/I distribution. The graphical representation 320illustrates traffic and angular correlation effects on C/I probabilitydensity. An interfering sector creates interference power I into aserving carrier sector with random carrier power C. The probabilitydensity for this pairwise sector interaction is accumulated as shown inFIG. 17 by weighting each locations' sample C/I probability density withthe traffic at that location. The sample location for a city is shown tohave a large traffic weighting relative to a sample location for aforest. Because there is a small difference in angle of arrivals for theforest example, there is a relatively high correlation between thecarrier power and the interference power due to similarities in thepropagation path traversed. This results in relatively less variabilityin the C/I sample for the forest as shown by the relatively tightdistribution in the graphical representation 320.

As previously described in conjunction with FIG. 16, frequency planparameters may be chosen, such as a sigma_fpp or standard deviation of 6decibels, and a maximum coefficient of 0.9 with a standard percentile of10 being chosen. In one embodiment, the weighting, as may be performedfor the distribution of each location sample C/I, may be performed inaccordance with a traffic map or Land Use Land Cover (LULC) map. Aspreviously described, the probability distribution for C/I in each pixelin the best server area may be determined assuming a lognormaldistribution which corresponds to cell fading and a particularinterferer. Distribution has been averaged over all pixels in the bestserver area. The percentile for distribution may be computedcharacterizing the pairwise C/I for the best server area in theparticular interferer. The average distribution may be formed using thecumulative probability distribution.

A measure of goodness of the assignment in terms of co-channel C/I isfound by assuming all channels are in use and that the interference fromeach sector using the same channel is that given by a pairwise C/Iestimate, as previously discussed in conjunction with the co-channel andadjacent channel C/I calculations.

Included below is a pseudo code description of the pairwise C/Icalculations as may be included in an embodiment.

form_pairwise_CtoI (pairwise_CtoI, percent_worse) for interferer =first_subsector to last_subsector for best = first_subsector tolast_subsector /** initialize cumul_dist */ for grid_point -first_grid_point to last_grid_point cumul_dist[best, grid_point] = 0read_path_list(interferer) /** get pixel maps, best server **/ for pixel= first_pixel[interferer] to last_pixel[interferer] best =best_server(pixel) if best < > NO_BEST_SERVER weight = traffic(pixel)/** compute mean E by computing difference between C and I values fornormal distribution **/ mean = server_power_dB(pixel) -interferer_power_dB (interferer, pixel) cor = correlation(best,interferer, pixel) /* sigma is standard deviation **/ sigma =DEFAULT_SIGMA * SQRT(2(1-cor)) grid_value = GRID_START for grid_point =first_grid_point to last_grid_point /** compute probability density **/cumul_dist[best,grid_point] = cumul_dist[best,grid_point] + weight *cumulative(grid_value, mean, sigma) grid_value = grid_value +GRID_SPACING for best = first_subsector to last_subsector threshold =percent_worse * total_traffic(best) grid_point = first_grid_pointgrid_value = GRID_START /** threshold is the percentile **/while(cumul_dist[best,grid_point] < threshold and grid_point <=last_grid_point) grid_point ++; grid_value = grid_value + GRID_SPACINGpairwise_CtoI[interferer, best] = grid_value

With regard to the foregoing pseudo code, a number of assumptions havebeen made about the available ancillary functions. In particular, thefunction read_path_loss(sub_sector) makes available the path loss forall the pixels that are sufficiently close to a given subsector togetherwith associated ranges of pixels. The functioninterfere_power_dB(sub_sector, pixel) uses the path loss previously madeavailable by read_path_loss to compute the received power from a givensubsector at the given pixel. The function server_power_DB(pixel) alsocomputes the received power at the given pixel. Here, the transmittingsubsector is the best server for that pixel. The corresponding path lossis not made available by a call to read_path_loss. The function traffic(pixel) gives the traffic for a given pixel which is assumed to beallocated to the best server subsector for the pixel. Recall thattraffic relates to a weighted use of population information. Thefunction total_traffic (sub_sector) gets the total traffic supported bythe given subsector. It is assumed that this is equal to the total ofthe traffic for all the pixels for which the given subsector is the bestserver.

It should also be noted that the forgoing pseudo-code forms anunnormalized cumulative distribution function. The percentile thresholdis normalized rather than the distribution function simply because inthis particular embodiment it requires less computation. However, otherembodiments may vary from this by using techniques known to thoseskilled in the art for each particular implementation. The normalizationfactor given by the foregoing function total_traffic (best) is not equalto the sum of traffic given by the function traffic (pixel) this isbecause the pixels within the range of a given interfere need notinclude all the pixels for a given best server area. It should also benoted that omitted pixels are not explicitly treated in the abovepseudo-code. The omitted pixels for example correspond to pixels forwhich the means C/I should be very large. If they were included in theabove pseudo code the shape of the cumulative distribution function maybe affected only at the high end. This omission thus effects thepercentile only when the C/I is large so that it does little more thanindicate that there is effectively no interference from a correspondingsubsector.

A note should also be made regarding the correlation. When thepropagation path from the desired signal and the interferer are nearlyidentical, the lognormal fading of the two are highly correlated.Consequently, the standard deviation of the resulting C/I distributionis reduced. The technique for finding the angle between two propagationpaths may use the angle to compute the correlation coefficient. In oneembodiment, the angle between the two directions of arrival is computedusing vector projection. Another embodiment may use the law of cosineswhich may be more computationally intensive than using vectorprojection. Subsequently, correlation is now a linear function of theangle when using vector projection, interpolating between a “peak value”at 0 degrees, and zero at 180 degrees. In one embodiment, such as in theGRANET embodiment, the configuration tool may be “hardwired” to use afor peak value of 0.9 for correlation coefficient. Recall, that acorrelation coefficient with a peak of 0.9 for a maximum was previouslydescribed in conjunction with box 314 of FIG. 16 for the particularimplementation of the described herein.

It should be noted that a pairwise C/I calculation previously describeduses the ratio of carrier strength to the strength of an interferingsignal for a second sector assuming the second sector is transmitting onthe same frequency as the first sector. Techniques have been describedwhich take as input traffic map or LULC information, as well as bestserver area path loss information, site, sector, and as well as antennainformation. The foregoing techniques produce a C/I matrix representingthe pairwise C/I calculations for a particular pair of sectors. Also aspreviously described in the foregoing, the pairwise C/I calculations asmay be store for example in the C/I matrix are used in producing totalor power sum C/I calculations. The total C/I may be computed for aco-channel assignment and/or adjacent channel assignment representingthe ratio of the carrier power from the server on a channel to the powerof all interfering signals on that channel or on adjacent channels.Total C/I may be computed for the following sets of channel assignmentsincluding, but not limited to, voice channels, signaling channels, voicechannels with the same SAT, and signaling channels with the same DCC.Inputs used computing the total C/I calculations in frequency planningare the assigned frequencies per sector in the pairwise C/I calculation.

A C/I map may be generated from completed frequency plans. Generally, aspreviously described the C/I map represents, given a pixel in aparticular best server area, the propagation functionality being used toestimate the received power from the best server and from all possibleinterferers. The sector with the strongest of these interferers isidentified together with corresponding C/I ratio. Recall, that the C/Iratio is the difference in decibels between desired signal andinterference.

Two different forms of C/I maps may be formed. For co-channel C/I, theinterference comes from any sector that is assigned or any channelassigned to the best server. For adjacent channel C/I interference comesfrom any sector that is assigned any channel adjacent to a channelassigned to the best server. For the C/I map computations, the inputsinclude frequency planning or assignments as well as path lossinformation. Using the foregoing C/I techniques, a C/I map may be outputfor the strongest interferer in the particular interfere.

It should be noted that the total C/I is meaningful in the context of aparticular frequency plan and may be computed for example by summing thepreviously computed pairwise C/I values directly. Summation may beformed as though there are constant C/I values by summing them.

Referring now to FIG. 18, shown is flowchart of an example of anembodiment of a method of performing channel assignments. FIG. 18 showsan example of a technique for performing frequency assignments 206, asmay be included in the flowchart 200, step 206 of FIG. 14. Generally,flowchart 206 of FIG. 18 shows general steps of one embodiment of howinput requirements and channel assignments may be used with respect tototal C/I calculations in determining whether or not to perform aparticular channel assignment.

At step 230, quality of service (QOS) input requirements may be obtainedor calculated as needed, such as those related to C/I calculations (i.e,co-channel C/I and adjacent channel C/I). At step 232, a channel and asector are selected. At step 234 a determination is made with respect tothe particular channel and sector at step 232. A determination is madeat step 234 as to whether, for each channel assignment, is the total C/Ifor that channel assignment greater than the QOS requirements. In otherwords, at step 234 a test is made considering the total C/Irequirements, such as co-channel and adjacent channel C/I, to determinewhether or not this channel assignment is acceptable by resulting in atotal C/I computation above a predetermined QOS requirement, such assignal strength. If a determination is made at step 234 that the totalC/I is greater than the quality of input, control passes to step 238where the channel assignment is made. Otherwise, control passes to step236 where the channel assignment is not performed. In other words, adetermination has been made by proceeding to step 236 not to perform achannel assignment because predetermined QOS input constraints have notbeen met.

At step 240, a determination is made as to whether channel assignmentsare complete. If so, control proceeds to step 242 where the channelassignments are complete and the channel or frequency assignmenttechnique stops. Otherwise, if channel assignments are not completecontrol proceeds to step 232 to the top of the loop where a new channeland sector are chosen.

Referring now to FIG. 19, shown is a flowchart of a method of anotherembodiment for performing channel assignments. It should be noted thatthe flowchart in FIG. 19 may be used, for example, as an alternative tothe methods steps of FIG. 18 when performing channel assignments.Generally, FIG. 19 shows a more generalized technique for performingchannel assignments in accordance with criteria that effects bothchannel and sector selection. In an embodiment, the technique of FIG. 19may be preferred over that of FIG. 18 since the method of FIG. 18 doesnot perform any adjustment to the criteria using feedback. Rather, FIG.18 performs a selected channel assignment or fails to do so inaccordance with C/I calculations and QOS input. In other words, FIG. 18either fails or succeeds for a selected channel assignment.

At step 250, initialization is performed, for example, of any variablesused in performing subsequent steps. At step 252, a sector is selectedusing sector selection criteria (SSC). Generally, SSC sets forth certainrules that may be used to select a particular sector. Various SSCs aredescribed in paragraphs that follow in conjunction with other Figures.At step 234, a channel is selected using frequency selection criteria(FSC). Generally, FSC are rules which assist in selecting a particularfrequency to be associated with a sector selected at step 252. At step256, a test is made as to whether more requests for channel assignmentsas may be input may be filled. If a determination is made at step 256that more requests may be filled, control proceeds to step 252 whereanother sector and channel are selected. If a determination is made atstep 256 that more requests cannot be filled, a determination is made atstep 260 as to whether all requests that have been made are filled. Inother words, at step 260, a test is made to determine whether all therequested channel assignments have been made. If a determination at step260 is made that all the requests have been filled in accordance withinput configuration parameters, control proceeds to step 262 where themethod of FIG. 19 ends. If at step 260 it has been determined that allrequests have not been filled in accordance with input configurationdata, at step 264 criteria adjustment is used to adjust the requestedfrequency assignments or input configuration parameters usinginformation from previous considerations. Control then proceeds to step252 where another sector and channel are selected.

It should be noted that the general flow of FIG. 19 takes into accountvarious channel requests made, for example, in the form of inputconfiguration data. In other words, as previously described, a requestas to the number of channels that may be associated with each particularsector may be made via input configuration data. At times, it may bedetermined that it is not possible to satisfy all of the assignmentrequests in accordance with input configuration parameters. At thispoint, rather than have the method of FIG. 19 fail, certain criteria areused to adjust the requested assignments producing a modified set ofrules for SSC and FSC.

The foregoing technique of FIG. 19 is an assignment technique using asector ordering in accordance with criteria to make decisions aboutchannels that are assigned once the sector is chosen. This criteriaimproves the overall assignment. Additionally, the foregoing techniquetakes into account past history from failed assignments and redoingrequested assignments in accordance with information about prioriterations. Generally, two steps over all needed assignments areperformed and then feedback information is used that may be obtainedfrom prior iterations. The flowchart shows the basic flow of theassignment technique. The combination of a frequency and sectorconstitutes an assignment of a frequency to a sector that will not beremoved unless further iterations are needed. At the end of theiteration, criteria used to make sector and frequency choices during theprocess, such as at steps 252 and 254, are automatically updated usinginformation about the assignment acquired from prior iterations. Once afrequency is assigned to a sector, the sector is closer to filling itsrequest requirements.

As will be described in conjunction with selection criteria, perhaps ona subsequent iteration, a different sector may be chosen as the sectorcandidate for the next assignment as an alternative, for example, toattempt another assignment to the same sector. The sector selectionprocess may be applied considering the effects of the most recentassignment. For example, the newly assigned frequency may reduce thepool of frequencies available for assignment to some of the sectors andcreate adjacent and co-channel interference to frequencies in othersectors. Consequently, the taking into account this sector assignment insector selection criteria may yield a different decision for the nextsector.

If there are still unfilled requests at the end of execution of the loopof FIG. 19, selection criteria may be changed as in step 264 usinginformation acquired from prior assignment iterations. Unfilled requestsmay be relatively difficult to fill in accordance with criteria used tomake assignment decisions. Thus, in subsequent iterations, criteria maybe modified in step 264 to give priority to the relatively moredifficult sectors at the expense of the relatively easy sectors.

Referring now to FIGS. 20A, 20B, and 21, shown is an example of anembodiment of the different criteria that may be used as in performingthe method steps for FIG. 19 for channel assignments.

Referring to FIGS. 20A, 20B, example criteria is set forth in the table400. The table 400 includes sector selection criteria (SSC) 410,frequency selection criteria (FSC) 420 and criteria adjustment selection422. Each of these portions of information 410, 420 and 422 mayrespectively be used in their appropriate processing steps of FIG. 19.For example, sector selection criteria 410 includes two sector selectioncriteria SSC1 and SSC2. Sector selection criteria may be presented insome type of hierarchical arrangement, for example, where the SSC1criteria is known to be simple and easier to calculate than those atsubsequently higher criteria levels such as SSC2. For example, the SSC2criteria 412 involves frequency separation constraints and C/Iconstraints and calculations. The C/I constraints, for example, may bethe co-channel and adjacent channel total C/I calculations as previouslydescribed. Similarly, the frequency selection criteria portion 420includes performing various calculations as may be involved in differentconstraints. For example, the FSC1 423 includes examining C/I orfrequency separation constraints. Thus, use of FSC1 includes performingC/I calculations, for example, such as the total co-channel and adjacentchannel C/I calculation as well as considering the frequency separationconstraints as may be represented in the channel separation matrix.

It should be noted that various criteria, such as SSC1, which takes intoaccount a “bias” that is an accumulated bias over past iterationsdetermined by criteria adjustment. In other words, “bias” represents afeedback metric or learning quantity as may be used as a weightingfactor when choosing a particular sector. This bias may be increased ordecreased with regard to whether a sector has had recent difficulties inprior iterations. This bias is updated in the adjustment criteria 422.Thus, the bias being adjusted in step 264 of FIG. 19 may result in alearning process and feedback for subsequent selections of sectors andchannels as performed in steps 252 and 254, respectively, in accordancewith criteria 410 and 420.

Referring now to FIG. 21, shown is an additional example of sectorselection criteria 430 which includes SSC3 and SSC4. It should be notedthat the SSC3 criteria includes a parameter identifying an allowablenumber or desired shortage. This desired shortage may be defined torepresent a threshold or percentage level identifying a maximumacceptable shortage with regard to the number of requested channels fora particular sector. For example, for sector A, 10 channels may berequested. The shortage threshold, as used in SSC3, may be 20% level or2 channels. Thus, this parameter states that even though 10 channelassignments for Sector A may be preferred or ideal, if this cannot beaccomplished with regard to performing channel assignments for thenetwork, as little as 8 channel assignments is acceptable for sector A.Use of this additional threshold shortage specifies a minimum level ornumber of acceptable channels for a sector. In effect, this allows theselection criteria to perform channel assignments using a range ofacceptable channel assignments for a sector.

It should be noted that using this shortage percentage or shortagethreshold may be used as an alternative to techniques which eithersucceed or fail. In other words, this shortage threshold provides for arange of acceptable configurations rather than a binary indication ofsuccess or failure for a single set of channel requests.

It should also be noted that this threshold value may be useful ininstances, for example, when an impossible configuration is initiallyrequested. In other words, an initially requested channel assignmentrequest may be impossible to produce in accordance with constraints.Thus, having a shortage threshold may allow the channel assignmenttechnique to possibly find other acceptable alternatives.

It should be noted that other embodiments may include one or more of theforegoing selection criteria for frequency and sector selection as wellas different adjustment criteria, such as bias, that are used andupdated when performing subsequent sector and channel selections. Otherembodiments may use different criteria than that which has beendescribed in the example tables in FIGS. 20A, 20B, and 21. Any one of avariety of different criteria known to those skilled in the art may beused in conjunction with the general feedback process shown in FIG. 19.

It should be noted that the bias used in the foregoing description andfigures may refer to a bias that represents an integer quantity. Otherembodiments may include a bias expressed in a different numeric or otherform. It should also be noted that the FSC and SSC may both be adjustedusing the same global bias. Alternatively, an embodiment may use a firstbias for FSC and a second different bias for SSC.

Referring now to FIG. 22, shown is an example of an embodiment of atable 440 showing various combinations of the previously displayselection criteria in accordance with differently rated levels ofcomplexity. For example, complexity option zero in this example is theless complex option with regard to the calculations involved with SSC1and FSC1. At the other end of the spectrum of the information in thetable 440, complexity option 4 includes the most complex calculations,for example, involving SSC2 and FSC3. Accordingly, in an implementationof the channel assignment technique as previous described, a user mayselect a level of complexity, (e.g., 0 through 4), without gettinginvolved in the particular frequency or sector selection criteria.Rather, an intuitive approach is taken by rating the differentcombinations of frequency and sector selection criteria with the variouscomplexities or time computations that may be required in performing thesector and frequency selections.

The foregoing techniques may use complex criteria requiringcomputationally intensive calculations for performing and evaluatingchannel assignments. Generally, as known to those skilled in the art,the channel assignment problem is an N-P complete problem. Further,calculations such as those included in performing C/I calculations maybe very computationally time consuming. Thus, it may be desirable tochoose specific SSC and/or FSC in accordance with this timeconsideration. In other words, in effect, the amount of time is a costor constraint to be considered when determining the level of complexityof the selection criteria used in the channel assignment techniques.

In one embodiment, an acceptable amount of time or time threshold may beused. This time threshold may be expressed in, for example, but notlimited to, an amount of CPU time, an amount of elapsed time, or otherform.

Referring now to FIG. 23, shown is a flowchart of an example of anembodiment of a method for determining selection criteria to be used inperforming channel assignments. The flowchart 750 includes steps thatmay be used to estimate the time in performing channel assignments usingcertain selection criteria. At step 752, a time estimate and selectioncriteria are determined. These may be input, for example, from a usersuch as via an input file including values for these items.Alternatively, these may also be specified interactively, as viakeyboard or other input selection. For example, a time threshold of 3days (72 hours) and using SSC3 and FSC3 may be selected. At step 754, atime estimate for one iteration or one channel assignment technique inaccordance with selection criteria is determined. This may performedusing various estimation techniques. In one embodiment, a singleiteration may actually be performed which performs one channelassignment to one sector. At step 756, a total time estimate is obtainedby multiplying the single time estimate from step 754 to arrive at atotal time estimate in accordance with the channel assignments to bemade for all sectors in the network. At step 758, a determination ismade as to whether the total time estimate is within the acceptable timethreshold determined at step 752. If it is, control proceeds to step 762where the selection criteria is deemed “acceptable” in accordance withthe time threshold. Otherwise, control proceeds to step 760 where newselection criteria is determined. The new selection criteria is thenestimated in accordance with steps formed by the loop previouslydescribed. It should be noted that an embodiment may also specify athreshold to be used in arriving at a time estimate in terms of thenumber of loop iterations to perform a channel assignment. It shouldalso be noted that variations of the foregoing flowchart 750 may be madein other embodiments. For example, an additional step may be includedallowing a user to re-enter a time threshold since after severalfailures, a user may realize that an unrealistic time threshold wasentered that will not result in any criteria being deemed acceptable foruse.

What will now be described is a technique that may be used in generatingcolor code assignments, such as DCCs or SATs, using channel assignmenttechniques. Color codes as previously described may be used indetermining which sector is responsible for a signal received at amobile unit. Generally, a channel assignment may be reused, for example,such that two or more sectors operate at the same channel or frequency.Use of a color code in combination with a channel frequency is onetechnique that may be used to distinguish between signals generated bythese two or more sectors. A color code may be chosen for each frequencythat is reused. Thus, a color code may be selected for a sectorassociated with a channel since the channel is used multiple times.

Assigning color codes may be done with a variation of the previouslydescribed channel assignment techniques. In the previously describedchannel assignment techniques, QOS input including constraints may beinput to the configurator 12. For a color code assignment, there aremodifications to these inputs previously described.

One modification is in the C/I calculations. The total co-channel C/Iand total adjacent channel C/I formulas are modified to includereference to a color code “1”. Referring now to FIG. 24, shown is anexample of an embodiment of formulas including the color code in the C/Icalculations. In particular, formula 900 represents the total co-channelco-color code C/I calculation, and formula 902 represents the totaladjacent channel co-color code C/I calculation as may be used in colorcode assignments. This will be described in more detail in paragraphsthat follow.

Another modification that may be included involves the channelseparation matrix. In this embodiment, the channel separation matrixrepresents a color code separation matrix. In this use, the channelseparation matrix is tightened. In particular, for each entry in thematrix which represents a common neighbor having a zero in the matrixentry, it is replaced with a 1. Recall that a zero indicates that twosectors could be assigned or use the same frequency. Replacing the zerowith a 1 indicates that the same color code cannot be used for sectorsassociated with the matrix entry. Generally, common neighbor refers tothe sector B that is a common neighbor to both sectors A and C. In otherwords, sector B may be handed off a signal from both sector A and sectorC. A portion of the constraint or channel separation matrix may be usedas will also be described in more detail in paragraphs that follow.

Referring now to FIG. 25, shown is a flowchart of an example of a methodfor performing color code assignments. In the following description, themodified C/I formulas and modified constraint matrix are referred to andrelated to steps of the color code assignment technique.

At step 922, a current channel variable “i” is assigned the firstchannel requiring color code assignments. Control proceeds to step 924where sectors having channel i assigned to it and channels currentlyhaving color codes are assigned are identified. As a result of step 924,two subsets of sectors are identified. A first subset of sectors arethose sectors associated with channel i requiring a color codeassignment on this loop iteration. A second subset of sectors are thosesectors associated with an adjacent channel to channel i, (e.g., channeli−1 and i+1) and pre-existing assignments, in which the sector alreadyhas a color code associated with the sector.

At step 926, pairwise C/I values are determined. In one embodiment, thepairwise C/I values are a submatrix or subset of the previouslydescribed C/I matrix. This submatrix may be represented by a squarematix having a dimension that is equal to or less than the existing C/Imatrix previously described. This submatrix includes those pairwise C/Ivalues having subscripts of sectors i,j corresponding to sectorsidentified in step 924. In other words, for every pair of sectors i andj identified in step 924, the pairwise C/I values corresponding tosubscripts i,j and j,i are included in the submatrix. If this firstembodiment of the pairwise C/I values is used, the modified cochanneland adjacent channel total C/I formulas 900 and 902 may be included andused in performing color code assignments in step 930, which isdescribed in following paragraphs.

A second embodiment of step 926 determines pairwise C/I values byadjusting a portion of the pairwise C/I values as may be included in thepairwise C/I matrix. In particular, the pairwise C/I values for thoseadjacent channel sectors as identified in step 924 are adjusted. The C/Ivalues correspond to those values associated with the second subset ofsectors identified in step 924. These C/I values are adjusted by apredetermined value. In one instance this predetermined value may be thedifference between the co-channel and adjacent channel thresholds thatmay serve as QOS inputs in a channel assignment process. If this secondembodiment of the pairwise C/I values is used, the channel assignmenttechnique which assigns the color codes to the sectors performs suchthat the comparison of the total C/I adjacent channel threshold testalways succeeds. Additionally, the similar total co-channel C/Ithreshold test takes into account the co and adjacent channel C/I byusing the adjusted C/I values just described.

Generally, step 926 takes into account filtering of a signal bytransmitters and receivers. This may be performed, for example as in thesecond step 926 embodiment, by adding to the pairwise C/Is thedifference between co-channel and adjacent channel constraints.

At step 928, a subset constraint or channel separation matrix is formed.This constraint matrix is also a subset of the previously describedchannel separation matrix. This subset channel separation matrixproduced as a result of step 928 may include the more stringent channelseparations for those sectors identified in step 924. Alternatively, thesubset channel separation matrix may include a subset of the originalchannel separation matrix without being modified to include morestringent channel separations. It should be noted that this subsetmatrix may be used in step 930 in determining color code assignment.

Control proceeds to step 930 where a channel assignment technique isused to assign color codes to sectors. In a channel assignmenttechnique, frequencies or channels, and sectors are the two sets ofitems being associated. Alternatively, in this instance for color codeassignments, there is a set of color codes to be assigned, and a set ofsectors to which these may be assigned. The set of color codes is theset of all possible color codes available. The set of sectors are thosesectors produced as a result of step 924, the first subset of sectorswhich are associated with channel i and require a color code assignmenton this iteration using the channel assignment technique at step 930.

At step 932, a determination is made as to whether all channels orfrequencies have been processed. If so, control proceeds to step 934where the method 920 stops. Otherwise, control proceeds to step 936where “i” is assigned the next channel for which color codes areassigned.

It should be noted that the foregoing suggests modifications to thechannel assignment technique to assign or associate color codes withsectors. The following summarized some of the analogous items and stepspreviously described as used in channel assignment and the color codeassignment elements.

Channel assignment Color code assignment A. associates a sector with achannel A. associates a color code with a sector B. a sector is chosenfrom a set of sectors B. a sector is chosen from a set of sectorsrequiring channel assignment requiring a color code assignment for thechannel currently being examined C. a channel is chosen from a set ofsystem channels C. a color code is chosen from a set of system colorcodes D. channel separation matrix D. subset of channel separationmatrix (note may include modified separation values) E. pairwise C/Ivalues E. subset of pairwise C/I values (note may include adjusted C/Ivalues or just subset of original values.

While the invention has been disclosed in connection with preferredembodiments shown and described in detail, their modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present inventionshould be limited only by the following claims.

What is claimed is:
 1. A method executed in a computer system forperforming channel assignments in a cellular network, the methodcomprising: selecting a first set of selection criteria in accordancewith a desired level of computational complexity; and determining achannel assignment in accordance with the first set of selectioncriteria, wherein selecting the first set of selection criteriaincludes: determining a first time estimate for a single channelassignment in accordance with the first set of selection criteria;determining a total time estimate using the first time estimate; andcomparing the total time estimate with a predetermined time threshold.2. The method of claim 1, further comprising: determining a second setof selection criteria based on comparing the total time estimate withthe pre-determined time threshold.
 3. The method of claim 2, wherein atleast one of the first and second set of selection criteria includesfrequency selection criteria.
 4. The method of claim 2, wherein at leastone of the first and second set of selection criteria includes sectorselection criteria.
 5. The method of claim 1, wherein determining thefirst time estimate comprises: performing a total carrier tointerference calculation.
 6. The method of claim 1, wherein determiningthe first time estimate comprises: adjusting a bias used in determiningsubsequent channel assignments.
 7. The method of claim 6, whereinadjusting comprises: adjusting the bias based on comparing the totaltime estimate with the pre-determined time threshold.
 8. The method ofclaim 1, wherein determining a channel assignment comprises: selectingone or more assignment criteria from a plurality of assignment criteriaoptions; and determining the channel assignment using carrier tointerference values and a predetermined threshold in accordance with theone or more assignment criteria, the carrier to interference valuesbeing determined by considering carrier signal strength and interferencesignal strength when both the carrier and the interference signalsoperate at a first frequency, the predetermined threshold representing aquality of service criteria.
 9. The method of claim 8, furthercomprising: using the carrier to interference values in evaluating oneor more channel assignments for a cellular network.
 10. The method ofclaim 8, further comprising: using a first set of carrier tointerference values and a second set of carrier to interference valuesin evaluation of alternative channel assignments.
 11. The method ofclaim 1, wherein the first set of selection criteria include frequencyselection criteria.
 12. The method of claim 1, wherein the first set ofselection criteria include sector selection criteria.
 13. The method ofclaim 1, wherein determining a channel assignment comprises: performinga total carrier to interference calculation.
 14. The method of claim 1,wherein determining a channel assignment comprises: adjusting a biasused in determining subsequent channel assignments.
 15. A methodexecuted in a computer system for determining channel assignments, themethod comprising: selecting a set of assignment criteria from aplurality of assignment criteria options; determining for each pair ofsectors included in a cellular network whether each pair are probableneighbors; determining pairwise carrier to interference values for eachpair of sectors including a first and a second sector if the pairwisecarrier to interference values are included in the selected set ofassignment criteria, the first sector having a carrier value and thesecond sector having an interference value, the first and second sectorsoperating at the same frequency; and using the probable neighbors andthe pairwise carrier to interference values in determining whether toperform a channel assignment for the cellular network, the channelassignment associating one or more channels with each sector included inthe cellular network.
 16. The method of claim 15, further comprising:determining contiguous regions for servers in accordance with geographicareas; determining total and common boundary measurements for eachsector included in the servers, the total boundary measurementrepresenting a boundary surrounding the geographic area associated witheach sector, the common boundary measurement representing a boundarycorresponding to a geographic area common between one of the pairs ofsectors; and determining if one of the pairs of sectors are probableneighbors in accordance with the total and the common boundarymeasurements associated with the one pair of sectors.
 17. The method ofclaim 16, wherein, for each pair of sectors including a first and asecond sector, the method further comprises: determining a first ratioof a common boundary common between the first and the second sectors toa total boundary for the first sector; and comparing the first ratiowith a first predetermined boundary threshold.
 18. The method of claim17, wherein for each pair of sectors, the method further comprises:determining a second ratio of a common boundary common between the firstand the second sectors to a total boundary for the second sector; andcomparing the second ratio with a second predetermined boundarythreshold.
 19. The method of claim 18, further comprising: determiningthat the first and the second sectors are probable neighbors based oncomparing the first ratio with the first predetermined boundarythreshold and the second ratio with the second predetermined boundarythreshold.
 20. The method of claim 19, wherein the first and secondpredetermined boundary thresholds are the same.
 21. A method executed ina computer system for performing channel assignments in a cellularnetwork, the method comprising: selecting a first set of selectioncriteria in accordance with a desired level of computational complexity;and determining a channel assignment in accordance with the first set ofselection criteria, wherein determining the channel assignment includes:selecting a set of assignment criteria from a plurality of assignmentcriteria options; determining, in accordance with the set of assignmentcriteria, pairwise carrier to interference values for each pair ofsectors including a first and a second sector, the first sector having acarrier value and the second sector having an interference value, thefirst and the second sectors operating at the same frequency; anddetermining total carrier to interference values by combining one ormore pairwise carrier to interference values.
 22. The method of claim21, wherein the total carrier to interference values include aco-channel carrier to interference value and an adjacent channel carrierto interference value.
 23. The method of claim 22, wherein theco-channel carrier to interference value is computed as:$\left( {C/I} \right)_{j,i} = \frac{1}{\sum\frac{1}{\left( {C/I} \right)_{k,{j\quad {pairwise}}}}}$

wherein the summation is for all k such that channel i is assigned tosector k.
 24. The method of claim 22, wherein the adjacent channelcarrier to interference value is computed as:$\left( {C/I} \right)_{j,i} = \frac{1}{\sum\frac{1}{\left( {C/I} \right)_{k,{j\quad {pairwise}}}}}$

wherein the summation is for all k such that sector k is an adjacentchannel being one of channel i−1 or channel i+1.
 25. The method of claim21, further comprising: performing frequency assignments to two or moresectors in accordance with the total carrier to interference values anda predetermined threshold.
 26. The method of claim 21, whereindetermining pairwise carrier to interference values comprises:determining a probability density for each portion of a best serverarea; weighting the probability density in accordance with cellularnetwork traffic associated with portions of the best server area; anddetermining a pairwise carrier to interference value in accordance witha percentile of the probability density.
 27. The method of claim 21,wherein the first set of selection criteria include frequency selectioncriteria.
 28. The method of claim 21, wherein the first set of selectioncriteria include sector selection criteria.
 29. The method of claim 21,wherein determining the channel assignment comprises: performing a totalcarrier to interference calculation.
 30. The method of claim 21, whereindetermining the channel assignment comprises: adjusting a bias used indetermining subsequent channel assignments.
 31. A computer programproduct for determining channel assignments, the computer programproduct comprising: means for selecting a set of assignment criteriafrom a plurality of assignment criteria options; means for determiningfor each pair of sectors included in a cellular network whether eachpair are probable neighbors; means for determining pairwise carrier tointerference values for each pair of sectors including a first and asecond sector if the pairwise carrier to interference values areincluded in the selected set of assignment criteria, the first sectorhaving a carrier value and the second sector having an interferencevalue, the first and the second sectors operating at the same frequency;and means for using the probable neighbors and the pairwise carrier tointerference values in determining whether to perform a channelassignment for the cellular network, the channel assignment associatingone or more channels with each sector included in the cellular network.32. The computer program product of claim 31, further comprising: meansfor determining contiguous regions for servers in accordance withgeographic areas; means for determining total and common boundarymeasurements for each sector included in the servers, the total boundarymeasurement representing a boundary surrounding the geographic areaassociated with each sector, the common boundary measurementrepresenting a boundary corresponding to a geographic area commonbetween one of the pairs of sectors; and means for determining if one ofthe pairs of sectors are probable neighbors in accordance with the totaland the common boundary measurements associated with the one pair ofsectors.
 33. A computer program product for performing channelassignments in a cellular network, the computer program productcomprising: machine executable code for selecting a first set ofselection criteria in accordance with a desired level of computationalcomplexity; and machine executable code for determining a channelassignment in accordance with said first set of selection criteria,wherein machine executable code for determining the channel assignmentincludes machine executable code for selecting a set of assignmentcriteria from a plurality of assignment criteria; machine executablecode for determining, in accordance with the set of assignment criteria,pairwise carrier to interference values for each pair of sectorsincluding a first and a second sector, the first sector having a carriervalue and the second sector having an interference value, the first andthe second sectors operating at the same frequency; and machineexecutable code for determining total carrier to interference values bycombining one or more pairwise carrier to interference values.
 34. Thecomputer program product of claim 33, wherein the total carrier tointerference values include a co-channel carrier to interference valueand an adjacent channel carrier to interference value.